Current, accurate fuel consumption measurements are extremely important for modern test rigs for internal combustion engines. It is a fact that fuel consumption is adversely affected by temperature fluctuations in the fuel circuit. Such temperature fluctuations are primarily due to changes in temperature of the internal combustion engine when in stationary operation, whereas the measured results taken during a stationary operation are reliable. Such changes in temperature can hardly be avoided although in the forward line of the fuel circuit there are provided devices for conditioning the fuel temperature, more particularly a cooler as well as a heater. The time-related changes in temperature lead to changes in the density of the fuel and thus changes in the fuel volume in the circuit while the volume of the line system remains constant. The fuel quantity which is supplied from a tank and which is recorded at a consumption measuring point in a supply line is reduced if there occurs a temporary increase in temperature due to an increase in the volume of the fuel in the system, whereas if there occurs a reduction in temperature and thus a reduction in volume, an increased quantity has to be supplied through the consumption measuring point, compared to the actual quantity consumed by the internal combustion engine.